It is known to provide metal to metal seals to carry out a wide variety of sealing operations within tubing such as surface fluid pipe lines and well tubing of an oil or gas well. Such metal to metal seals are complex, expensive to manufacture, must be preformed and often result in permanent deformation so that the seals cannot be reused. Also, it is known to provide resilient seals which do not provide metal to metal sealing in such tubing, are cheap and which are reusable, however, such resilient seals have disadvantages that they do not have the strength of metal to metal seals and cannot be used in aggressive environments which degrade the seal.
Furthermore, it is known to provide a wide variety of tools for carrying out well operations within tubing of a well, such as an oil or gas well, the tools requiring a seal to enable specific well operations to be carried out. Examples of such tools include tubing hangers, packers, bridge plugs, straddles, gravel-pack packers and the like. Each of such tools are often complex, including many interrelated parts, and require complex running, support, activating/deactivating and retrieving tools to achieve sealing and allow the well operation to be carried out using the tool. Furthermore, complex operations are often required to be performed in order to locate, activate/deactivate and/or retrieve the tools.
Similar problems are encountered with tools provided in tubing such as gas or oil pipelines located above ground.
Disadvantages associated with such tools are therefore the relative complexity of the tools, the complexity of the operations which are required to be carried out in order to locate, activate/deactivate and/or retrieve the tools, and the abovementioned disadvantages of presently known seals.
An annular seal is disclosed in U.S. Pat. No. 6,182,755 (Mansure) which includes a collapsible bellows. The bellows is expanded for insertion downhole to reduce its outer diameter and is set by compaction to provide a seal or anchor. However, the seal of U.S. Pat. No. 6,182,755 is not initially rigid, which will create problems during running in and tripping out of a borehole, when the seal is in the expanded position. Also, the bellows itself requires support through support shoulders to provide an effective seal/anchor; whilst embodiments are disclosed without such support shoulders, such would be unlikely to provide an effective seal/anchor in harsh downhole environments.